A study will be conducted to determine the therapeutic efficacy and safety of long term oral administration of the bile acid, chenodeoxycholic acid for the dissolution of cholesterol gallstones in asymptomatic patients. This will be carried out as a double-blind, randomized, controlled trial by cooperating medical centers. Concomitantly, fundamental research studies will be performed on the mechanisms of gallstone formation and dissolution which shall contribute to basic knowledge of gallstone disease.